Spell Rotation

The guild I'm in tackled her for the first time last night, learning as we went. Unfortunately, we learned the winning tactic just as the timer ran out on our hold of Tol'Barad. But, since we came so utterly close (5% I think it was?) I believe we have the right strategy, we just need to work on execution.

Spec

I recommend using an Arcane spec with Mage Armor and the Mage Armor glyph. You're going to have to deliver a shockingly high and continuous amount of AoE damage and spamming Arcane Explosion is just the ticket because it's instant cast and effectively costs no mana. I'm able to continuously blast those out without any loss of mana because I recover the amount I spend as soon as I spend it, thanks to the armor and glyph. As well, if you're late to the party and not to the center of the rally point in time, you can spam AE as you enter. It's instant cast so move and blast, don't you know.

Markers

We set out too many rally markers at first (as subsequent screenshots will show) but these three seem to be the best. And, truth be told, we could also boil it down to one.

Use all three while learning the fight

The blue one is the most important.

Yellow and green are useful when learning the fight but I think you'll find it OK to forgo them in subsequent encounters.

Blue is your Eye Rally Point.

Eyes phase

This battle is all about the eyes. During the fight, Occu'thar will release Eyes of Occu'thar. These are eyes that fly out from his body and zoom onto each person in the raid. They're about the same size as the Sleepy Willy pet beholder. Everyone in the raid gets one and they do tremendous damage—then they do even more damage if they're alive after 10 seconds. So, the entire raid must destroy all eyes within 10 seconds or the fight becomes untenable.

That means everyone has to group up and allow everyone's AoE attack to benefit the entire raid. People tackling their own eyes individually won't work—at all. It's a group exercise.

We chose to all gather at the blue raid marker when the eyes came out. If, however, that location was on fire (see below) then we would choose yellow or green, depending on circumstance.

Blue and purple are not good places to be

As you can see, the fires are fairly large.

What I was doing, and it seemed to work OK, was to gather at the rally point, place a Flamestrike, then spam Arcane Explosion like there was no tomorrow.

But there's a problem

Stacking together can kill the entire raid in seconds.

What Occu'thar likes to do is spray death ray lasers onto one (random) member of the raid and a terrific fire erupts from that point on the floor. As illustrated...

"Focus Fire" attack

If everyone is stacked together to deal with future Eye attacks, then the entire raid will be killed. What to do?

Spread out then stack up

Start the encounter spread out—but not too far. What you, as a mage, want to do is to be within Blink range of your raid's eye rally point (we chose the center of the grate and that seemed to work well) and, ideally, also 12 meters away from everyone else. That can be very tough to position and, frankly, you'll have time to get out of the Focus Fire radius even if it happens close to you—if you have proficient healing.

The key, though, is to anchor yourself relative to the rally point. That way, when the eyes come, you'll have a chance to Blink to the rally point and fully target and cast your Flamestrike around yourself just as the eyes appear and you can begin Arcane Explosions.

Timing

There are two—or three—episodes of Focus Fire then an Eye attack. It's easy to feel the timing of it, even without addons (which is my situation). Once we were surprised by a third Focus Fire attack, which killed the whole raid as we'd stacked for an imminent eye attack. So, there's still a bit of RNG that can wipe the raid.

Save your cooldowns for the eye attacks. If you can enter an eye attack at full mana so you have full damage—so much the better. This isn't a DPS race against Occu'thar so much as a kill-all-the-eyes-in-nine-seconds fight.